Preservation of butadiene polymers with mercaptals of hydroxy aldehydes



Patented Aug. 21, 1951 PRESERVATION OF BUTADIENE POLYMERS WITH MERCAPTALS' OF HYDROXY ALDE- HYDES Robert L. Sibley, Nitro, W. Va., assignor to Monsanto Chemical Company, St. Louis, Mo., a cor poration of Delaware No Drawing. Original application January 1'7,

1945, Serial No. 573,317. Divided and this application September 21, 1948, Serial No. 50,434

The present invention relates to a method of preserving butadiene polymers and to the products obtained thereby. The invention particularly relates to preserving rubbery polymers prehardening and embrittlement ofsynthetic rub- -14 Claims. (Cl. 260-457) bery polymers of conjugated butadiene hydrocarbons. Still other objects will in part be particularly pointed out in the detailed description following and will in part be apparent.

pared by the polymerization of a material con- '5 In accordance with this invention it has been sisting predominantly of a conjugated butadiene discovered that acetals and mercaptals of hydrocarbon. hydroxy aldehydes are valuable preservatives for The properties of rubber and rubbery like a rubber. The preservatives of this invention polymers which are unique and which render possess the general formula them useful and in many cases essential for industrial purposes are their capability of being H/ greatly extended under stress coupled with the R C property of forcibly retracting to approximately x-R,

their or1g1na1 SIZE and shape after the stress 1s where R is an hydroxy substituted organic removed. Many rubber articles must undergo radicle, R1 is an organic radicle, R2 is an organic durmg us? a Very large number of dlstomons radicle or H and X is sulfur or oxygen Merand recoveries. .under quite wide ranges of temcaptals and acetals of the sugars are particug t conphtmns In the'case me larly efiicacious preservatives and are therefore ers failure is hastened by the deter orating efrefe red The $568 the g neral f0 mula fects of air or oxygen. While synthetic rubbery p I y W s e r conjugated butadiene polymers are more re- R1 sistant to oxidation than natural rubbers, they OHZOHKHOEDHC are peculiarly susceptible to deterioration through the efiects of heat and especially heat in the 26 X R2 presence of air or oxygen. The hardness of the where X R1 and R2 have the Same significance polymer increases and it tends to become brittle as before'and n is an integer with the result that it loses to a substantial de- Typical examples of aceals and mercaptals gree its capability of being extended without rupof hydroxy aldehydes which may be employed in ture. Apparent1y failure is not due solely t the practice of this invention comprise glucose oxidation 511108 the change takes place 1n spi 30 'diisoamyl mercaptal, glucose diethyl mercaptal, of the presence of the usual antioxidizing cata-. .glucose ethylene mercaptal, arabinose dibutyl lysts. While .natural rubbers also exhibit this ljfimercaptal glyceraldehyde diethyl mercaptal, W of deteriorstlon the efiect 1s 9 less h glucose diisoamyl acetal, glucose diethyl acetal, serlous because the natural Product orlgmally salicylaldehyde dimethyl acetal, salicylaldehyde possesses a greater capability of being extended dibutyl mercaptal, glycol aldehyde dimethyl acetwithout rupture so that although the absolute a1, glycol aldehyde dibutyl acetal, glucose s- V e P the loss m b as great theraged ethyl O-methyl monothio acetal, galactose diethyl uct stlu retains reasonably Satisfactory elastic .monothio acetal, glucose dibutyl monothio acetal, properties. For this reason a preservative which t hydroxy propionaldehyde diethyl meta], will prevent or retard this loss of elastic proper-'40 alpha, hydroxy propionaldehyde diethyl acetal, ties in synthetic conjugated butadiene polymers t hydroxy propionaldehyde dibutyl mercaptal, 1S partlclllally f ijlalpha hydroxy propionaldehyde dibutyl mercap- An Object of the invention is to improve tal, beta hydroxy propionaldehyde dibutyl acetal, Synthetlc nju t d butadiene p lymer. Ap ralpha hydroxy propionaldehyde dibutyl acetal, ti ula j t s to p s v a Sy thetic conjualdol diethyl acetal, aldol diethyl mercaptal, a d u di p r andfp s u l aldol dibutyl acetal, aldol dibutyl mercaptal, f o r O jec is t0 p d a Class O glucose mono butyl acetal, glucose mono methyl s r p se vi d mprovi g the properacetal. The mono acetals are also known as ties of a synthetic conjugated butadiene polymer. glucosides. Another object is to increase the flex life of a 6 Methods of making mercaptals and acetals are butadiene-l,3 hydrocarbon polymer and in genwell known and are described in the literature. eral to increase the useful life of vulcanized prod- However, methods for preparing the preservatives ucts prepared from such polymers. A still of this invention are illustrated below although further object is to prevent or inhibit heat it is to be understood that the invention is not limited thereto. V.

Example I Substantially 100 parts by weight of dextrose (0.55 molecular proportions) were carefully mixed with 100 parts by weight of concentrated hydrochloric acid, sp. g. 1.19. 'The mixture was cooled to about C. and substantially 100 parts by weight (1.11 molecular proportions) of n-butyl mercaptan were gradually added to the cold mixture. An exothermic reaction set in immediately and the desired mercaptal precipitated from solution. After stirring for a short time the white crystalline product was filtered oif, washed and dried. The crude glucose dibutyl mercaptal melted at 127 and after recrystallizing from alcohol the M. P. was 133 C.

Example II Substantially 50 parts by weight of anhydrous dextrose (0.27 molecular proportions) was mixed with substantially 40 parts by weight of mercapto ethanol (0.51 molecular proportions). The mixture was cooled to 20 C. and 60 parts by weight of concentrated hydrochloric acid and sp. g. 1.19 was added with cooling. The charge was stirred at 2-6 C. for several hours and the clear solution allowed to warm up to room temperature. After diluting with 79 parts by weight of ethyl alcohol, the acid present was neutralized with basic lead carbonate and the salt cake filtered off, washed with alcohol and the filtrate and washings combined. The alcohol and water were then distilled off under reduced pressure. The residue was a thick viscous liquid believed to be glucose dihydroxy ethyl niercaptal. It was obtained in excellent yield and exhibited highly desirable preservative action as hereinafter described.

Example III Substantially 100 parts by weight of dextrose removed, preferably by distillation under vacuum. The residue was a very thick clear viscous syrup believed to be a mixture of glucose butyl acetals. When incorporated into butadiene polymers it imparted the desirable properties hereinafter described.

As specific embodiments of the invention which illustrate the invention but are not limitative thereof stocks were compounded comprising:

Base stock,

7 parts by weight Copolymer of butadiene-1,3 and styrenek 100. Carbon black ..s 40.

Zinc oxide 3. Saturated hydrocarbon softener 8. Sulfur s 1.75 N-cyclohexyl 2-benzothiazole sulfenamide 1.2

1 GR-S rubber.

From the base stock compositions were prepared as follows:

Amount. Stock Preservative Parts by Weight A Glucose dibutyl mercaptal 3 B Glucose diisopropyl mercaptal 3 C Glucose di n-propyl mcrcaptal. 3 l? Glucose diethyl mercaptal..... 3 .h Glucose butyl aeetal mixture. 3 F Glucose dihydrox'y ethyl meroapt 3 G Glucose di tolyl mercaptal 3 H Glycol aldehyde diethyl acetal 3 The stocks so compounded were cured by heating in the usual manner in a press at 142 C. and the vulcanized products were then artificially aged by heating in circulating air for 24 hours in an dven at 100 C. The modulus and tensile properties of the vulcanized products before and after aging Stock are set forth below.

Table fg l g g Tensile at Ult. Tensile at at Elonga- Brew 1n 31mg" at E1011 a- Break in P lbs/m. Per Cent tion 6 lbs/in! g tion of 300% Una'ged to min. cure Aged min. cure 1,000 a, 140 20 1, 555 2,080 365 770 2, 555 680 845 2, 820 625 785 2. 550 635 945 3, 310 000 795 a, 075 680 1, 040 2, 510 430 750 a, 050 700 0 a, 040 630 570 2, 525 140 930 2. 705 555 955 a, 120 520 1. 110 2, 880 520 7 5 2,535 605 870 s, 000 can 605 2, 910 750 1. 050 s. 050

U'iiaged90'inin. cure Agedmin. cute p 2, 320 650 900 a, 120 700 2,810 650 790 3, 110 90 910 3. 135 635 695 2, 920 680 790 a, 010 645 525 2, 780 660 825 a, 020 510 925 3.130 500 1, 130 2, 050 550 780 a, 500 s 2, 950 540 555 2, 700 680 940 2, 820 595 Again, practice of this invention is not limited to the specific compositions given above, such compositions being merely illustrative of the manner of employing the preservatives of this invention. They may be employed in conjunction with other vulcanizing agents than those mentioned for this invention is applicable to compositions of polymers of conjugated butadiene hydrocarbons of most varied nature. Other accelerators and activators may be employed with varying differences in tensile and modulus properties but still exhibiting the desirable properties of the class. While about three percent by weight based on the copolymer of the new preservatives is about the optimum amount, smaller amounts as for example one percent, may be used and desirable preservation thereby effected. Amounts in excess of about three percent can be used but generally without increased benefit. The usual method of treating the polymer is to incorporate the preservative into the polymer by milling or similar procedure but other means may be employed. For example, the preservative may be added to a dispersion of the polymer.

This is a division of co-pending application Serial No. 573,317 filed January 17, 1945, now U. 8. Patent 2,468,307.

What is claimed is:

1. The method of preserving a rubbery polymer prepared by the polymerization of butadien 1,3 and styrene which comprises incorporating into the preformed polymer 1-3 percent based on the polymer of a mercaptal of a hydroxy aldehyde.

2. The method of preserving a rubbery polymer prepared by the polymerization of butadiene-1,3 and styrene which comprises incorporating into the preformed polymer 1-3 percent based on the polymer of a sugar mercaptal.

3. The method of preserving a rubbery polymer prepared by the polymerization of butadiene-1,3 and styrene which comprises incorporating into the preformed polymer 1-3 percent based on the polymer of a compound of the structure where 11. is an integer and the Rs are aliphatic chain radicles.

4. The method of preserving a rubbery polymer prepared by the polymerization of butadiene- 1,3 and styrene which comprises incorporating into the preformed polymer 1-3 percent based on the polymer of a compound of the structure S-R cmomononno where n is an integer and the Rs are aryl radicles of the benzene series.

5. The method of preserving a rubbery polymer prepared by the polymerization of butadiene-l,3 and styrene which comprises incorporating into the preformed polymer 13 percent based on the polymer of a mercaptal of an hydroxyl aliphatic aldehyde.

6. The method of preserving a rubbery polymer prepared by the polymerization of butadiene-1,3 and styrene which comprises incorporating into the preformed polymer 1-3 percent based on the polymer of a compound of the structure where the Rs are aliphatic chain radicles.

7. The method of preserving a rubbery polymer prepared by the polymerization of butadiene- 1,3 and styrene which comprises incorporating into the preformed polymer 1-3 percent based on. the polymer of a compound of the structure.

CH2OH(CHOH)4 mer of a mercaptal of a hydroxy aldehyde.

9. The vulcanized rubbery polymer of the copolymerization product of butadiene-1,3 and styrene preserved by having incorporated into the preformed polymer 1-3 per cent based on the polymer of a sugar mercaptal.

10. The vulcanized rubbery polymer of the copolymerization product of butadiene-1,3 and styrene preserved by having incorporated into the preformed polymer 1-3 percent based on thepolymer of a compound of the structure where n is an integer and the R's are aliphatic chain radicles.

11. The vulcanized rubbery polymer of the copolymerization product of butadiene-1,3 and styrene preserved by having incorporated into the preformed polymer 1-3 percent based on the polymer of a compound of the structure S-R cmomonomnc S-R where n is an integer and the Rs are aryl radicles of the benzene series.

12. The vulcanized rubbery polymer of the copolymerization product of butadiene-1,3 and styrene preserved by having incorporated into the preformed polymer 1-3 percent based on the polymer of a mercaptal of an hydroxy aliphatic aldehyde.

13. The vulcanized rubbery polymer of the copolymerization product of butadiene-l,3 and sty- *rene preserved by having incorporated into the S-R where the Rs are aryl radicles of the benzene series.

ROBERT L. SIBLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 80,4 5 Stewart July 21, 1945 2. 5 S e art Jul 1. 1 5 

1. THE METHOD OF PRESERVING A RUBBERY POLYMER PREPARED BY THE POLYMERIZATION OF BUTADIENE1,3 AND STYRENE WHICH COMPRISES INCORPORATING INTO THE PREFORMED POLYMER 1-3 PERCENT BASED ON THE POLYMER OF A MERCAPTAL OF A HYDROXY ALDEHYDE. 